New models of tiny, wireless pacemakers are undergoing clinical trials in Duke hospitals.
The two models, the Nanostim leadless pacemaker and the Micra transcatheter pacing system, are smaller than AAA batteries and do not require the long electrical wires, or leads, placed inside the heart with traditional pacemakers. Leadless pacemakers also eliminate the need for surgical incisions and lower the patient's risk for infection and bleeding. Duke is one of 50 places in the world conducting these trials, which are open to patients with atrial fibrillation or an irregularly slow heartbeat.
“These studies are designed to answer how effective [the pacemakers] work long term—we’re very impressed so far,” said Dr. Brett Atwater, a cardiologist and investigator in the Nanostim trial. “Leadless pacemakers have the potential to completely change the pacemaker in the U.S. I think more than half will be leadless over the next decade, so this first study is an important step towards that.”
One of the major advantages of the new pacemakers is the relative ease of implanting them. Traditional pacemakers require a surgical incision to place a pulse generator about the size of a silver dollar underneath the collarbone, Atwater explained. Wires between one and 1.5 feet long then have to be threaded around the heart to regulate electrical pulses.
The new models, however, are delivered through a catheter in the leg’s femoral vein up to the heart, eliminating the risk of infection from an incision. They also attach directly onto the heart with tiny hooks or screws, rather than with long leads—which have been known to clog veins, become embedded in heart tissue and cause other complications.
“Leads in pacemakers have always been the weak link,” said Dr. Jonathan Piccini, a cardiologist and investigator in the Micra trial. “These leadless devices eliminate the number one failing component of pacemakers today.”
The simpler implant procedure takes anywhere from 30 to 50 minutes and might lead to quicker patient recovery compared to the traditional pacemaker, which takes between 60 and 90 minutes to be inserted, Piccini explained. Patients also like how the new pacemaker leaves no unsightly lump under their skin, Atwater said.
The Micra trials are pending approval by the Food and Drug Administration, and the Nanostim trials are ongoing in Duke hospitals.
Although these models can only pace a single chamber of the heart, the companies that manufacture them—St. Jude Medical and Medtronic—are working on developing dual-chamber models, Atwater said.
“It’s a minority of patients that are eligible, but it’s an important minority,” Piccini said. “An analogy is the first hybrid vehicles that weren’t popular and today maybe still don’t have a broad appeal, but the importance of this therapy is that it signifies a paradigm shift.”
Pacemakers have used leads to regulate the heartbeat since the 1970s, Piccini explained, so these new models represent a potentially sweeping change to the field.
“Maybe in the future, we’ll have [a pacemaker] in the top chamber and one in the bottom and they’ll communicate wirelessly, or maybe they’ll be even smaller,” he said. “The point being, they’re ushering in a new era where we’re beginning to really experiment with technology to eliminate the difficulties in pacing with leads.”
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